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A 

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SYLLABUS 



A COURSE OF LECTURES 



GEOLOGY. 



Rev. a. SEDGWICK, M.A., V.P.R.S., &c. 

WOODWARDIAK PROFESSOR 
OF THE UNIVERSITY OF CAMBRIDGE. 



THIRD EDITION. 



CAMBRIDGE: 

PRINTED BY JOHN W. PARKER, UNIVERSITY PRINTER. 
PUBLISHED BY 

J. & J. J. DEIGHTON, AND T. STEVENSON, CAMBRIDGE ; 
AND JOHN W. PARKER, LONDON. 



M.DCCC.XXXVn. 




0.£ 
IU7 



SYLLABUS. 



PART I. 
Chapter I. — Introduction, 

1. Great subdivisions of the materials com- 
posing the surface of the Earth — organized — 
unorganized. 

2. Further subdivisions — separation of the 
various branches of Natural History — distin- 
guished from Natural Philosophy. 

3. Geology — its objects, and place among the 
physical sciences. 

4. Modes of considering the mineral kingdom 
— separation of Geology and Mineralogy. 

5. Recent discoveries in Geology — changes in 
the physical surface of the earth and in the 
animal kingdom — connection established between 
Geology and other branches of Natural History. 

6. Ancient speculations on the theory of the 
Earth false and defective — "Sacred Theories" in 



the same manner false and defective — Examples 
derived from the writings of Burnet, Woodward, 
&c. 

7. True mode of conducting Geological Spe- 
culations. 



Chapter II. 

2%e great inequalities presented hy the surface 
of the Earth. 

1. Separation of land and water. 

2. Inequalities of the land — mountains — valleys 
— plains. 

3. Mountain chains — secondary ridges. Valleys 
— principal — secondary — longitudinal — trans- 
verse, &c. &c. 

4. Mountains — their external forms the result 
of many causes — the agency by which they were 
produced — the nature and position of their com- 
ponent rocks — the different degrees of degrada- 
tion, &c. &c. — Examples derived from Sections. 

5. Bearings and escarpments of different mount- 
ain chains. 

6. Relations of mountain chains to each other 
— great physical divisions of the Earth's surface. 

7. Further subdivisions — manner in which the 
waters are drained from the Earth's surface. — 



The great physical regions of the Earth subdi- 
vided into River Basins. Examples. 

8. Ramifications of the rivers in contiguous 
basins generally distinct — in some instances in- 
osculate — remarkable examples. 

9. Subdivisions of River Basins — rare exam- 
ples of bifurcations in the higher part of river 
channels. 

10. Basins of rivers generally bounded by 
mountain chains — Exceptions — Example of rivers 
which cut through mountain chains — of rivers 
unconnected with great elevations, &c. General 
illustration of the drainage of England — Con- 
clusions. 



Chapter III. 

On the great agents hy which the Earth's sur- 
face is modified; and on the effects which 
have been produced hy them during known 
periods. 

§. 1. Modern Alluvial formations. 

1. Atmospheric movements, and laws by which 
they are effected. 

2. Ascent of vapour — laws effecting its dis- 
persion and precipitation. Consequent formation 
of rivers— degradation of the land, &c. 



a2 



3. Formation of springs. Various modifica- 
tions of them. Examples derived from the neigh- 
bourhood of Cambridge, &c. 

4. Plane of Congelation — effects produced by 
its oscillations in Alpine regions — avalanches, 
glaciers, &;c. 

5. Degradation produced by mountain torrents 
— by the bursting of mountain lakes. Parallel, 
roads of Glen Roy — Floods of the Drave, &c. 

6. Progress of rivers through mid regions — 
rare bifurcations. 

7. Reproductive power of rivers in their de- 
scent to low regions — frequent bifurcations — for- 
mation of deltas and various causes of their in- 
crease and diminution. Examples from the deltas 
of the Rhine, the Nile, the Ganges, and the 
Mississippi. 

8. Laws by which the Earth's surfice is modi- 
fied from the effects of vegetable life — modifica- 
tion of deltas — turf bogs — subaqueous forests — 
floating islands, &c. 

9. History of the Drainage of the Bedford 
Level — Practical conclusions. 

10. Organic Remains of alluvial deposits. 

11. Chemical action of the elements — decom- 
position of rocks — chemical deposits. 



J. 2. Action of the Sea. 

1. Action of the Sea, in wearing down the 
solid parts of the globe. Examples. 

2. Progress of the tidal wave — Marine currents 
— great equatorial current. 

3. Distribution of incoherent matter at the 
bottom of the sea — soundings of the German 
Ocean, &c. 

4. Changes by the operations of marine ani- 
mals — shell beds — coral reefs. — Examples. 

5. Changes in the relative place of the sea 
level — recent elevation of land. — Examples: 
Norway — coasts of Devonshire and Cornwall, 
&c. 

6. Sand floods on the sea coast — formation of 
downs — sand floods of desert countries. 

7. Time during which the above-mentioned 
physical agents have been at work — natural 
chronometers — difficulties in their application. — 
Examples. 

J. 3. Products and Effects of Volcanic Action. 

1. Earthquakes — great extent to which they 
are propagated — indications of deep-seated vol- 
canic action — precede volcanic eruptions, &c. — 
Examples :— Monte-Nuovo (1538) ; Lima (1746) ; 
Jorullo(1756); Iceland (1783); Riobamba(1797); 
St Vincent (1812), &c. &c. 

2. Volcanos — great extent of their action — 
Examples from the works of Humboldt, &c. 



8 

3. Their number — linear arrangement — geo- 
graphical distribution, &c. 

4. Volcanic craters — composition and form — 
relations to other formations — craters of Eleva- 
tion. 

5. Eruptions, (i) Vapours — (2.) Ashes ; 
sand ; pumice ; volcanic bombs ; fragments of 
lava; of rocks, sometimes unaltered, &c. — 
Streams of melted lava from the lips or side 
of the crater. 

6. Currents of lava — their fluidity — heat — ve- 
locity — modification in passing from a fluid to a 
solid state, extent, &c. — Examples. 

7. Streams of mud not originating in the 
crater — their origin. 

8. Eruptions of mud, &c. — Examples — some- 
times accompanied with bituminous matter, fish, 
&c. 

9. Greatest eruptions after long intervals of 
repose. Historical view of the eruptions of Ve- 
suvius, &c. 

10. Degradation of craters — by atmospheric 
action — by earthquakes — by the slow chemical 
action of volcanic vapours, &c. 

11. Structure of lavas — scoriaceous — vesicular 
— glassy — stony — earthy — brecciated. Experi- 
ments of Watts — Basaltic and trachytic lava — 
Obsidian — Pearl-stone — Pumice, &c. 

12. Volcanic minerals — their origin — great 
number of species. 



9 

(1.) Sublimated in volcanic vapours and 

deposited in crevices; 
(2.) Crystallized from a state of igneous 

fusion ; 
(3.) Formed by aqueous infiltration. 

13. Increase of temperature below the surface 
— primeval fluidity made probable by the form 
and internal structure of the earth. 

14. Theories of volcanic action — seat of vol- 
canic fires — Uncombined metallic bases of the 
earths — shifting of isothermal planes, &c. 

15. Volcanic products, unconnected with any 
existing crater — their origin determined ; 

(1.) By their mineral structure; 
(2.) By their geological relations ; 
(3.) From the effects produced by their 
junction with other rocks. 

16. Application of these rules to formations of 
Basalt — Examples — Basaltic Rocks of Auvergne, 
&c. 

17' Effects of volcanic action in changing the 
relative level of land and water. Examples. 

18. Changes in the relative level of land and 
water proved by the distribution of coral reefs. 

19. Raised Beaches on the coast of Devonshire 
and Cornwall — similar phenomena on the coast of 
Norway, &c. 

20. Proofs of igneous action, and of successive 
changes in the relative level of sea and land, among 
rocks of all geological epochs. 



10 



Chapter IV. 

Ancient alluvion {''Diluvial detritus'') — includ- 
ing all superficial transported aqueous deposits 
which are unconnected with the present mechan- 
ical action of the waters. 

1. This alluvion distinguished generally from 
common alluvial detritus by its antiquity — 
position — organic remains — not being in pro- 
gress of formation, &c. &c. 

2. Proofs of the former action of great denuding 
currents — forms of mountains — excavation of 
valleys — position of gorges, &c. — singular relations 
of many river channels to the elevated regions of 
the country. 

3. Further proofs, from the nature and position 
of the transported materials. Examples — 

(1.) Boulders of the Alps; 

(2.) Of the north-eastern plains of Europe ; 

(3.) Of the north of England. 

4. Stratified masses of old alluvion — successive 
epochs of its formation on the flanks of the 
Alps, &c. 

5. Organic remains. — (i.) In rolled masses 
derived from older formations. — (2.) Land and 
marine shells. — (3.) Bones of mammalia of extinct 
and living species, &c. &c. — No human bones (?) 

6. Description of some remarkable species. 

7. Great local deposits of bones. Examples. 

8. Ossiferous Caverns, Osseous Brucias, &c. 



PART II. 

Chapter I. 
J. 1. Internal Structure of the Earth. 

1. Observations by which the internal 
structure of the Earth is discovered. 

2. Strata — Their relations to each other — con- 
formable — unconformable — strike or direction — 
dip — inclination. Examples. 

3. Formations — natural groups having a com- 
mon origin during one uninterrupted period. 

4. Materials of which strata are formed — 
chemical — mechanical — or mixed. 

5. Elements which enter into the composition 
of rocks — great variety of natural combinations — 
Geological descriptions confined to such as are 
elaborated on a great scale. 

6. Simple minerals which enter into the compo- 
*sition of crystalline rocks — modes of determining 
their species. 

7. Examples — Quartz — Felspar — Mica — Talc 
— Chlorite — Hornblende— Augite — Schorl— Calc- 
spar, &c. &c. 



12 

8. Rocks — simple and compound. 

9. Structure — granular — slaty — porphyritic — 
amygdaloidal — columnar — globular, &;c. 

10. Rocks of double structure. 

11. Cemented rocks — of regular and irregular 
structure. 

12. Stratified and unstratified — limitation of 
these terms. — Conclusion. 

J. 2. Organic Remains — state in which they 
occur in various orders of strata. 

1. Ancient theories connected with their ap- 
pearance. 

2. Petrijhction — conditions necessary to it. 

3. Modes of reasoning on the former conditions 
and functions of fossil bodies. 

4. Animals vertebrate and invertebrate. 
Four primary divisions of the Animal 

Kingdom. 

(1.) Vertehrata. 
(2.) Mollusca. 
(3.) Articulata. 
(4.) Radiata. 

5. Organic remains, from each of these divi- 
sions, forming many classes, and orders. Ex- 
amples. 



(1.) Vertehrata. 



Mammalia. 
Aves. 
Reptilia. 
Pisces. 



13 



(2.) Mollusca. 



(4.) Radiata. 



Testacea — Bivalves — 
Univalves — Shells sin- 
j glechambered and mul- 
\ tilocular, &c. &c. 

{Crustacea. 
Arachnidea. 
Insecta. 

Echinodermata. 
Crinoidea. 

Zoophyta — including nu- 
merous genera of hard 
corals. 

6. Vegetable Kingdom. Primary divisions 
derived from the Emhryo, the Structure^ and 
the Fructification. 

iDicotyledones. 
Monocotyledones . 
Acotyledones. 
{ ExogencB. 
\ Endogenee. 
j Ductulosce. 
\ Cellulares. 

iPhanerogamcB. 
Cryptoga7n<E. 

7. Many genera and species of organic remains 
from each of these divisions. 

8. Importance of organic remains — in the 
identification of contemporaneous deposits — in 
determining the successive conditions of the Earth. 



(2.) Structure. 



(3.) Fructification. 



14 



Chapter II. 

Classification of Stratified Rocks. 

1. Stratified Rocks — Tertiary — secondary — 
primary. 

(a.) Tertiary class — including all regular 

deposits superior to the chalk, and older 

than the old alluvion of the neighbouring 

regions. 

{b.) Secondary class — three divisions — upper, 

middle, and lower. 

All regular deposits com- 

Upper Division. < mencing with the Chalk 

and ending with the Lias. 

I New red sandstone — car- 
boniferous series — old red 
sandstone. 
Silurian system. 
Cambrian system. 
(c.) Primary class — all stratified rocks in- 
ferior to the preceding — often meta- 
morphic, and of very obscure relations. 



Lower division. \ 



15 



Chapter III. 

TERTIARY CLASS. 

J. 1. Estahlishment of successive groups. 

1. Relation of Tertiary groups to different 
inferior deposits, as exhibited in natural sections. 

2. Independence of different tertiary deposits, 
whether marine or fresh-water — difficulties in 
their classification — principles on which it is 
attempted. 

3. Two marine groups, superior to the Chalk, 
on the east coast of England. 

(i.) Upper group. — Crag of Norfolk, Suf- 
folk, and Essex. 

(2.) Lower group. — London Clay — Sand 
and Plastic Clay. 

4. Two groups on the south coast of England. 
( L) Upper group . — Alternation s of calcareous 

and argillaceous marls, generally lacas- 
trine ; but in the Isle of Wight contain- 
ing subordinate argillaceous bands, with 
a mixture of marine and fresh-water 
shells. 
(2.) Lower group — London Clay — Sand and 
Plastic Clay. 

5. Corresponding deposits of the Paris basin. 

6. Deposits on the Loire {Falun) superior to 
the highest group of the Paris basin. Corre- 



16 

sponding deposits in the basin of Bordeaux, and 
in the Cotentin — in the Superga, near Turin — 
Mont Ferrat, &c. 

7. Great Sub-Apennine deposits, superior to the 
preceding groups. 

8. Deposits, containing numerous shells and 
other organic remains of existing species, forming 
a connecting link between tertiary and modern 
deposits. — Examples. 

(1.) Raised beaches on the coasts of Devon- 
shire and Cornwall. 

(2.) Raised beaches on the coasts of South 
America. 

(3.) Newest marine deposits of Calabria and 
Sicily. 

9. Principle of classification, applicable to all 
the preceding groups — from which result four 
distinct periods of deposit, as in the following 
table: 

Raised beaches on va- 
rious coasts — newest 

/ ^ TkT m- marine deposits of 

(1.) Newer fltocene. { ^. ., i o i 

Sicily and Southern 

Italy — many local la- 

. castrine deposits, &c. 

' Sub-Apennine forma- 

rr.\ r\Tj nr tions — Craff of the 

(2.) Older Pliocene. \ ^ 

south-eastern coasts 

of England, &c. 



17 



(3.) Miocene. 



(4.) Eocene. 



Touraine — basin of 
Bordeaux — Superga 
near Turin — basin of 
.Vienna, &c. &c. 

Marine and lacastrine 
deposits of the Paris 
- basin and the Hamp- 
shire basin — London 
Clay, &c. &c. 



^.2. Description of the Crag and other upper 
tertiary groups — of the basins of Hamp- 
shire and London — and of the Paris hasin. 

(a.) Raised beaches, Crag deposits, S^c. 

1. Raised beaches of Devonshire and Cornwall 
— indications of serveral distinct movements — 
stratification — structure — organic remains of spe- 
cies found in the neighbouring seas. 

2. Other deposits with similar organic remains, 
in various parts of the British Isles and at dif- 
ferent levels. 

3. Bovey basin — its ancient outlet — stratifica- 
tion — organic contents — comparison with similar 
deposits. 

4. Crag deposits of the south-east coast of 
England — their place defined by the following 
descending section : 

(1.) Sand and gravel — bones of mammalia 
of extinct and living species. 



18 

(2.) Blue and brown clay, with many rolled 
masses of chalk and fossils drifted from 
older formations — bones of mammalia 
of extinct and living species — Elephant 
— Rhinoceros — Hippopotamus — Bea- 
ver — Deer, &c. 

(3.) Sand, often regularly bedded — alterna- 
ting with rolled flints — in its lower 
portion alternating with and passing 
into beds of shells, often broken or 
waterworn — rolled bones of mammalia 
— Mastidon — Elephant — Deer, &c. — 
{Upper Crag.) 

In Norfolk the preceding groups terminate 
in beds of silicious shingle resting on a 
waterworn surface of chalk. 

(4.) Lower or Coralline Crag of Suffolk — 

many fossils like the preceding. 
(5.) London Clay. 
5. Comparative antiquity of the Crag — proved 
by its place and organic remains. 

ih.) Basins of London and Isle of Wight. 

1. These basins once probably continuous — 
Great dislocations of the Chalk — outlying ter- 
tiary masses. 

2. Successive formations of the Isle of Wight 
Basin — enumerated in the ascending order, for 
their more ready comparison with the formations 
of the Paris Basin. 



19 

(1.) Sand and pJusfic ckiy — Sands of vari- 
ous colours, alternating with bands of 
grit — beds of pebbles — clay with calca- 
reous concretions, septaria^ and marine 
shells — Subordinate bands of potter's 
clay, lignite, &c. Sometimes beds of ma- 
rine and freshwater shells, mixed or com- 
minuted near the bottom of the series. 

(2.) London clay — -Clay with sepfaria — cal- 
careous sand-stone and green earth — 
rarely beds of coarse shell-limestone — 
&c. Numerous remains of marine shells 
— fish — turtles — Crustacea — wood — seed 
vessels, &c. &c. 

(s.) Sand with siliceous concretions, &c. 
Bagshot sand. 

(4.) Great complex deposit of shell lime- 
stone, indurated marl, unctions marl, 
clay, sand, &c. — generally lacastrine, 
but in the Isle of Wight containing 
subordinate argillaceous beds with a 
mixture of marine and freshwater shells. 
— Gyrogonites and other remains of 
plants — remains of fish — rarely bones 
of mammalia. 
3. London Basin — containing the three first 
divisions of the Isle of Wight section. 

(c.) Paris Basin. 

1. Natural separation into three principal 
groups. 

B 



20 

2. Ascending order of deposits established by 
Cuvier and Brongniart. 

(I.) Plastic clay and sand — occasionally con- 
taining lignite — interspersed freshwater 
shells, &c. 
(2.) Calcaire grassier. — Chloritic sand — 
coarse shell limestone — marl — clay, &c. 
— Innumerable marine shells — rarely 
freshwater shells — very rarely bones of 
mammalia. 
(3.) Siliceous limestone — sometimes passing 
into a variety of buhr-stone — partially 
covering and sometimes replacing the 
preceding group — rarely with freshwater 
shells. 
(4.) Gypseous deposits — subdivided into three 
systems of beds. 

(«.) Bands of indurated marl — slaty 

marl with menilite and gypsum 

— the lowest portion containing 

some marine shells. 

(6.) Gypsum beds with a little marl 

— Fossil fish — no fossil shells. 
(c.) Great Gypsum beds — lower part 
impure and siliceous — middle pris- 
matic — upper part alternating 
with marls. — Innumerable bones 
of mammalia, frequently of ex- 
tinct genera — bones of birds, 
fishes, and turtles. 



21 

(5.) Marl — separated into two formations : 

(«.) White calcareous freshwater marl 
— resembling that in the next 
inferior group. — Silicified remains 
of palm trees — freshwater shells, 
&c. 
(b.) Marine marls — yellow, with fish- 
bones and marine shells — green 
marls with balls of sulphate of 

strontian yellow argillaceous 

marls with fish-bones and ma- 
rine shells. The whole system 

surmounted by two oyster beds 
separated by a bed of white marl 
without shells. 

(6.) Sand and grit of great thickness — Sili- 
ceous beds, nodules, and calcareous con- 
cretions. In the upper portion concre- 
tions of various colours, sometimes cal- 
careous — casts of marine shells, &c. 

(7.) Buhr-stone — freshwater limestone, &c. 

(«.) Green or red sand and marl with 
beds and concretions of buhr- 
stone {meuliere) — without shells. 

{h.) Beds of compact or earthy fresh- 
water limestone — siliceous beds 
and concretions — resinous flint 
— buhr-stone, Gyrogonites, many 
freshwater univalves, &c. 
b2 



22 

3. General conclusions — separation of the pre- 

ceding groups into marine and freshwater 
formations. 

4. Other freshwater deposits of central France 
— extraordinary association with volcanic rocks, 
&c. 

5. Comparison of the formations in the basins 
of Paris and the Isle of Wight. 

6. On certain deposits which are superior to 
the upper chalk of England, and appear to be 
intermediate between the tertiary and secondary 
classes — Maestricht — shores of the Baltic — 
valleys of the Eastern Alps, &c. 



Chapter IV. 

SECONDARY CLASS. 

Upper division, including all the series from 
the Chalk to the Lias, inclusive. 

^. 1. Cretaceous series — subdivided into the com- 
plex groups of' the Chalk and Green Sand. 

1. Chalk. 

(i.) In England this group is subdivided 
into — 

(«.) Upper chalk — with numerous 
flints. 



23 

(h.) Lower chalk — with interspersed 

flints. 
(c.) Chalk marl — grey chalk — with- 
out flints. 
Examples of these subdivisions in various 

natural sections. 
(2.) Varieties of structure, colour, &c. — 
magnesian chalk — indurated chalk — 
granular chalk in contact with trap. 
(3.) Range — elevation — inclination — thick- 
ness remarkable localities soils 

springs, &c. 
(4.) Organic remains. 

2. Green Sand group. 

(1.) In England this group is subdivided 
into — 

(«.) Upper green sand — malm-rock — 

fire-stone. 
{h.) Gait — of Cambridge and Folk- 
stone. 
(c.) Lower green sand — Woburn 
sand — Kentish rag, &c. 
(2.) Varieties of mineral structure — changes 
from the suppression of one or more of 
the subdivisions — passage into and alter- 
nation with chalk- marl — In the lowest 
part of the third division (c.) shelly 
beds resembling portions of the oolitic 
series. 



24 

(s.) Range — extent— remarkable localities. 
(4.) Organic remains. 

3. Cretaceous series of the Continent — Planer 
Kalk. Quader Sandstein. 

4. General geographical distribution of this 
series — its character and elevation in the chains 
of the Alps and Pyrenees. Changes of structure, 
inclination, &c. 

5. General character of the organic remains in 
the cretaceous series. — Conclusion. 



J. 2. Weald Clay, Hastings Sand, and Purheck 
Limestone. 

A great complex deposit, chiefly of freshwater 
origin, breaking the continuity of the British 
secondary series. 

1. Weald Clay, {Oak-tree Clay.) 

(i.) Varieties of structure — subordinate bands 
of shell limestone (Petworth marble) 
with numerous Paludince — bands of 
grit covered with the Cypris fdba — 
— iron-stone, &c. — in the lower part 
separated by numerous bands of grit 
more or less ferruginous and passing 
into the lower group. 

(2.) Fossils, chiefly freshwater — alternations 
of marine and freshwater shells near the 
upper surface. 



25 

2. Hastings Sand, or Iron Sand. 
(i.) Varieties of structure — 

(«.) Grey calciferous sandstone some- 
times passing into a conglome- 
rate — sandy clay, &c. 
(h.) Sandstone — often friable and of 
a yellowish-white colour — some- 
times ferruginous. 
(c.) Sandstone with calcareous con- 
cretions — ^ferruginous sandstone 
— layers of iron-stone — varie- 
gated sandy clay — shale — Frag- 
ments of carbonized wood — 
lignite, &c. 
{d.) Argillaceous shelly limestone al- 
ternating with slaty argillaceous 
marls — abounding in shells of 
the genus Cyclas, &c. Forms a 
passage into the next group (?) 
(2.) Fossils. — Plants — shells chiefly fresh- 
water — Fish of freshwater genera — 
Crustacea — Gigantic carniverous and 
herbiverous reptiles — Pterodactyls, &c. 
"3. Purheck Limestone. 

(1.) Mineral structure — Marble with nume- 
rous Paludinae — shelly calcareous flag- 
stone — indurated marl — layers of argil- 
laceous marl — shale, &c. 
(2.) Fossils. — Numerous impressions of fish 
— fragments of turtles. — Freshwater 
and marine shells. 



26 

4. Limited extent of the three preceding groups 
— Contemporaneous deposits on the Continent. 

5. Condition of the region now occupied by the 
south coast of England between the period of the 
oolites and the commencement of the preceding 

series Dirt bed of the Isle of Portland — 

Cycadeoidece — Conifer (e in an erect position. — 
Conclusion. 

J. 3. Oolitic Series . 

1. Place of this series defined by natural sec- 
tions — character of the oolitic terraces — continuity 
of the great oolitic terrace. 

2. The series in the south of England made 
up of three groups of deposits containing oolitic 
limestone, each resting on a great bed of clay. 

3. Upper group — Portland Oolite, and Kim- 
meridge Clay: 

(1.) Portland Oolite formation. 

(«.) Thin beds of limestone — compact, 
earthy, and cellular — chert, &c. 
Very few fossils. 

(A.) Strong beds of oolitic limestone 
— mixed and alternating with 
masses containing numerous casts 
of shells — Turritell(je, Trigotiice, 
&c. &c. 

(c.) Beds of varied structure — hard, 
brown, splintery, cherty, &c. 
— White earthy beds with black 
flinty concretions — Fossils. 



27 

(2.) Kirnmeridge Clay. 

(a.) Sand and gritty beds alternating 

with clay (Kirnmeridge sand). 
(b.) Clay — shale, sometimes highly 
bituminous — numerous fossils — 
Ostrea deltoidea^ Gryphcea vir- 
gula — &c. &c. 
(c.) Clay — sometimes mixed with 
green earth — alternating with 
the upper calc-grit of the next 
inferior group — Ostrea deltoidea, 
&c. &c. 
(3.) Continuity of the Kimmeridge clay — 
gradual thinning of the Portland rock in 
its range towards the north. 
(4.) Varieties of mineral structure — range — 
inclination — elevation — thickness, &;c. 
4. Middle group — Coral Rag Oolite and 
Oxford Clay. 

(1.) Coral Rag Oolite. 

(a.) Irregular beds of shelly calc-grit 
— often ferruginous — sometimes 
alternating with the lower beds 
of Kimmeridge clay. 
(b.) Broken semicrystalline and 
earthy beds of limestone, some- 
times alternating or mixed with 
oolitic marl — abounding in shells 
and corals (Coral rag.) 
(c.) Oolitic freestone — often coarse 
and earthy — fragments of shells. 



28 

&c. — Mixed or alternating with 
masses like the preceding sub- 
division (b). 
(d.) Beds of calcareous-grit — sand 
and sandstone, sometimes high- 
ly ferruginous, &c. — Changes in 
the several subdivisions — gradual 
thinning of the formation in its 
range towards the north — its 
disappearance in a part of Cam- 
bridgeshire and Lincolnshire — 
re-appearance in Yorkshire. — 
Remarkable fossils. 
(2.) Oxford Clay. 

(a.) Great clay, with the Gryphcea 

dilatata — bands of sandstone and 

calc-grit — bituminous beds— sep- 

taria, &c. 

(b.) Irregular beds of micaceous sand- 

■ stone, calc-grit, &c. — (Kelloway 

rock.) 
(3.) Continuity of this formation — thickness 
— remarkable localities — modification 
of its structure in Yorkshire, &c. 
5. Lower or great Oolitic group and Lias Clay, 
(1.) Great Oolitic group. 

(«.) Cornbrash — earthy, loose, amor- 
phous beds of yellow, grey, and 
bluish shelly limestone. 
{h.) Slaty calcareous sandstone alter- 
nating with sand. 



* 



29 

(c.) Yeovil marble (Forest marble) — 

coarse slaty shelly limestone, 

sometimes alternating with beds 

of clay — marl — slaty calc-grit, 

'&c. 

(d.) Bradford clay. 

(e.) Great Oolite — Oolitic freestone 
of Bath, Ketton, &c. 

(Jl) Fuller's earth and sand. 

(g.) Inferior Oolite — Coarse brown 

oolitic limestone calcareous 

concretions — sand, &c. — Conti- 
nuity of this formation — thick- 
ness — changes and modifications 
of structure, by the suppression 
or expansion of one or more of 
the sub-divisions. Examples. 
(2.) Lias. 

(a.) Upper Lias clay. 

(b.) Marlstone Gritty micaceous 

marl, more or less indurated, of 
a greenish or yellowish brown 
colour; sometimes ferruginous. 

(c.) Lower Lias clay. 

(</.) Blue and white Lias — with Gry- 
phcea incurva, &c. — Continuity 
of the formation — thickness — 
changes of structure — first ap- 
pearance and gradual expansion 
of division (fl.)— Modification of 



30 

division (b.) — Minerals — mine- 
ral springs— extraordinary fossils, 
&;c. 

6. Oolitic series of the Yorkshire Coast. 

(1.) Kimmeridge clay. t 

(2.) Coral rag oolite, calc-grit, &c. 
(3.) Oxford clay and Kelloway rock. 
(4.) A complex carboniferous series, in which 
the types of the lower oolitic group 
of the south of England are almost 
entirely lost — subdivided into: 

(a.) Sandstone, shale, iron-stone, car- 
bonaceous beds,&;c. — surmounted 
by a band of impure shell lime- 
stone, sometimes oolitic. 
(b.) Impure limestone, sometimes 
oolitic — supposed from its fossils 
to be on the parallel of the Bath 
oolite. 
(c.) Sandstone, shale, coal, &c. — - 
resting on bands of shelly cal- 
careo-ferruginous sandstone. 
(5.) Lias — subdivided into : 

(a.) Upper lias shale (alum shale). 
(b.) Shale, iron-stone, and micaceous 

sandstone (marl-stone). 
(c.) Lower lias shale and lias — 
Grypheea incurva, &c. 

7. Re-appearance of the carboniferous groups 
of the oolitic series in Sutherland and the Hebrides 



31 

— extraordinary associations with basaltic rocks — 
coast-sections of the Isles of Sky and Mull. 

8. Great development of the oolitic series in 
France. 

(i.) Section on the coast of Normandy. 

(«.) Argile de Hotifleur (Kimme- 
ridge clay.) 

(ft.) Hard cherty limestone — coral- 
line oolite — calc-grit, &c. (Coral 
rag or middle oolite group.) 

(c.) Argile de Dives (Oxford clay.) 

(</.) Oolitic fissile shell limestone — 
Caen freestone — yellow calca- 
reous sandstone ferruginous 

oolite, &c. (Group of the great 
oolite.) 

{e.) Lias — Gryphcea incurva, &c. 
(2.) Section of the Oolites of Burgundy and 
the north-eastern Provinces. 

(«.) Light coloured compact lime- 
stone. (Portland rock.) 

(ft.) Grey marls and marly limestone, 
with the Gryphcea virgula. 
(Kimmeridge clay.) 

(c.) Compact and earthy limestone — 
coralline oolite, &c. (Coral rag.) 

(«?.) Grey marly limestone and calc- 
grit, with the Gryphcea dilaiato. 
(Oxford clay.) 



32 

(e.) Great plateau of oolitic lime- 
stone — yellowish marly lime- 
stone — entrochite limestone, &c. 
— (Group of the great oolite.) 
(jf.) Marl and Gryphite limestone. 
(Lias.) 
(3.) Sections in the south of France — 
gradual obliteration of the preceding 
subdivisions. 

9. Oolitic series of Germany — range, extent, 
&c. 

(1.) Section through the oolitic plateau 
between the Neckar and the Danube — 
lias — ferruginous oolite — dolomite — 
compact yellowish limestone — coral rag 
— Solenhofen slate, &c. 

(2.) Carboniferous series of the Porta West- 
phalica. 

10. Oolitic series of the Alps — great change 
of mineral structure — elevation — contortions — 
subordinate masses of rock-salt — peculiar fossils. 

11. Geographical distribution of the series — 
general character of the fossils — distribution of 
certain species — anomalies. Conclusion. 



33 



Chapter V. 

SECONDARY CLASS. 

Middle division, including netv Red Sandstone, 
Carboniferous series, and old Red Sandstone. 

§. 1. ^ew Red Sandstone series. 

1. Extension of the plain of the new red 
sandstone from the base of the great oolitic 
terrace of England — interruptions from the pro- 
trusion of the older formations — termination of 
the series towards the west. 

2. Relations of the series to the inferior and 
superior deposits exhibited in various natural 
sections. 

3. Subdivisions of the whole series, 
(i.) Yorkshire and Durham. 

{a.) Upper red, or variegated marl 
and gypsum. 

{h.) Red and variegated sandstone — 
with subordinate masses of red 
marl and gypsum. 

(c.) Thin bedded grey limestone — 
occasionally yellow cellular and 
magnesian — rarely with organic 
remains. 

{d.) Lower red marl and gypsum. 

(e.) Magnesian limestone — crystal- 
line compact — earthy — cellular 



34 

— oolitic — fetid — &c. — Occa- 
sionally with organic remains — 
Producta, Spirifer, Gorgonia, 
Retipora, <§c. 

(Jl) Thin bedded compact limestone 
(with Producta, Spirifer, &c.), 
resting on marl-slate with im- 
pressions of plants, and fish. 

{g.) Lower red sandstone — generally 
unconformable to the carboni- 
ferous series — sometimes con- 
formable and appearing to pass 
into the upper coal-grits — rarely 
with remains of plants. 

(2.) Coast of Cumherland. 

{a.) Red and variegated sandstone 
resting on red gypseous marls. 

{h.) Magnesian limestone — cellular, 
earthy, fetid, &c. 

(c.) Magnesian conglomerate — con- 
taining rolled masses of moun- 
tain limestone. 

{d.) Lower red sandstone — of consi- 
derable thickness — in some places 
unconformable to the coal mea- 
sures — a few stems of plants. 

(3.) Succession in a part of Warwickshire, 
{a.) Red or variegated marl and 
gypsum. 



35 

{b.) Red and variegated sandstone. 
(c.) Magnesian conglomerate — with 
rolled masses of mountain lime- 
stone—This portion ill developed. 
(d.) Lower red sandstone — of con- 
siderable thickness, containing 
subordinate calcareous beds, and 
passing into the coal measures 
through variegated marls and 
beds of freshwater limestone 
with coal-plants. 
(4.) Similar succession in Shropshire — 
the magnesian conglomerates better 
developed. 
(5.) Bristol Coal Fields and Valley of the 
Ex. 

(a.) Red or variegated marl, gypsum, 

&c. 
(h.) Red and variegated sandstone. 
(c.) Magnesian conglomerate with 
rolled masses of mountain lime- 
stone — no traces of the lower 
red sandstone as a distinct de- 
posit — the whole series resting 
horizontally on the inclined beds 
of the older formations. 
4. External character of the red sandstone 
country — changes of structure — forest-sand — 

conglomerates thickness minerals cobalt, 

manganese, calamine, rock-salt — fossils. 

V 



36 

5. External character of the magnesian limp- 
stone — varieties — remarkable localities — minerals 
and mineral springs — soils — &c. 

6. Great expansion of this series in Europe — 
constancy of minerals and fossils — exceptions. 

7. Series in Central Germany and Eastern 
France with their British equivalents. 

f Upper red marl 

(i.) Keuper or Marnes \ and gypsum — 

irisees, j saliferous marls, 

V &c. 

(2.) Muschel Kalk r Not discovered 

fossil limestone of \ in the British 

Luneville. ( series. 

^ ^ n ^ I ^ • ( Red and varie- 

(3.) Bunter-sanastem — \ 

^ V , . ' r-i ^ ) gated sandstone 
Gres bigarre, Gres (^ ° 



rouge. 



— new red sand- 
stone. 



(4.) Rauchwacke, Zech- / 

stein, &c. not much j Magnesian lime- 
developed in Eastern jl stone group. 
France. V 

i Marl-slate of 
Durham, with 
fish, &c. 
(6.) Rothe-todte-liegende j Lower red sand- 
— Gres des Vosges. \ stone group. 
8. Recent discoveries confirming the identity 
of the upper red marls, &c. with the Keuper 
and Marnes irisees. 



37 

9- Rock salt — in the Alps, Poland, &c. — 
not confined to the new red sandstone series — 
theories of its formation — Conclusion. 

§. 2. Great carboniferous series, including the 
mountain limestone. 

1. General character of the series — alterna- 
tions of limestone, sandstone, shale, ironstone, &c. 
with subordinate bands of coal. 

2. Relations of this series to the inferior and 
superior groups exhibited in sections. 

3. Varieties of limestone — crystalline — com- 
pact — earthy — magnesian — bituminous — fetid — 
rarely oolitic — beds abounding in encrinites, 
shells, and corals, &c. 

4. Varieties of sandstone — millstone grit — 
freestone — micaceous slaty sandstone — chert — 
beds more or less ferruginous, often marked and 
penetrated by leaves and stems of plants. 

5. Varieties of shale — common — bituminous, 
sometimes pasing into coal — sandy and micaceous, 
passing into bands of sandstone — calcareous and 
indurated (calp) — passing into shale-limestone, 
rottenstone, crow-limestone, &c. — subordinate beds 
and bands of ironstone — numerous impressions of 
plants. 

6. Varieties of coal — ^bituminous shale — bitu- 
minous coal anthracite mineral charcoal 

lignite — &c. — Impressions of carbonized plants. 

7. Great extent of this series in the British 
Isles — mode in which the several members are 

(:2 



38 

grouped together in diflPerent coal fields. 

Examples. 

Coalfields of Somersetshire , Gloucestershire ^ 
and South Wales. 

(1.) Upper and productive part of the series, 
subdivided into: — 
(a.) Upper coal field ; 
{h.) Pennant grit; 
(c.) Lower coal field ; 
Separated generally from the lower un- 
productive calcareous groups by beds of 
coarse sandstone — millstone grit — &c. 
(2.) Great mountain limestone group— un- 
productive — subordinate beds of sand- 
stone and shale — in the lower part 
generally separated from the old red 
sandstone by a deposit of shale — This 
group generally arranged in broken or 
continuous ridges — highly inclined — 
dipping towards a common centre, and 
forming the base of distinct coal-basins. 
Carboniferous series of Derbyshire. 
(i.) Great productive coal-field, surmounted 
by the terrace of the magnesian lime- 
stone. 
(2.) Millstone grit. 
(3.) Great shale and shale-limestone. 
(4.) Mountain limestone, interrupted by 
great irregular beds or tabular masses of 
trap — the base of the series not exposed. 



39 

Carhoniferoua series of a part of Yorkshire 
and Westmorland. 

(1.) Great upper coal field. 

(2.) Complex group of millstone grit shale 
and coal, in several alternations — some- 
times with bands of impure crow-lime- 
stone. 

(3.) Complex group, in which five deposits 
of limestone alternate with sandstone 
containing impressions of plants, and 
with beds of shale, more or less bitu- 
minous, containing two or three pro- 
ductive beds of coal, &c. 

(4.) Great scar-limestone with a few sub- 
ordinate bands of shale and sandstone — 
separated sometimes from the inferior 
system by a deposit of bituminous shale. 

The whole series sometimes rest imme- 
diately upon the inclined edges of 
greywacke — or conformably upon great 
beds of old red conglomerate. 
Carboniferous series of Northumberland. 

(i.) Great productive upper coal field. 

(2.) Great complex group — including mill- 
stone grit — limestone — shale with bands 
of impure coal — tabular masses and 
dykes of trap, &c. 

(3.) Lower productive coal field with sub- 
ordinate beds of limestone forming the 
base of the whole series — resting un- 



40 

conformably on greywacke — separated 
from the porphyry of the Cheviots by 
old red conglomerate. 

Carboniferous series of Ireland. 

(1.) Great complex contorted groups on 
the parallel of the upper English coal 
field. 

(2.) Widely extended horizontal deposits of 
mountain limestone alternating with 
shale and sandstone — in their lower 
portion passing into thin bedded argil- 
laceous limestone {calp) — resting con- 
formably on the old red sandstone. 

Carboniferous series of Scotland. 

(i.) Coal formations between the Firths of 
Forth and Clyde, on the parallel of 
the lower groups of Northumberland? 

(2.) Series of the Isle of Arran, &c. 

8. Remarkable foreign localities — absence of 
the formation in the Alps and Pyrenees — appear- 
ance of the coal fossils on the parallel of the lias. 

9. Origin of coal — comparison with some of 
the newer deposits of lignite — enumeration of 
the most remarkable coal plants. 

10. Enormous extent and rate of the present 
excavations in the British Isles — first commence- 
xnent — probable duration, &c. 

11. External character of coal countries — 
minerals — mineral springs. 



41 

12. External character of mountain-limestone 
countries — minerals and mineral waters — ravines 
— caverns — intermitting springs — soils — &;c. 

13. Characteristic fossils — Conclusion. 

J. 3. Old Red Sandstone and Conglomerate. 

1. Great extent of this group in the British 
Isles — Its relations to the inferior and superior 
systems exhibited in various natural sections. 

2. Mineral structure. Red conglomerates — 
beds of red and variegated sandstone — of micaceous 
flagstone {tile-stone) — rarely of red gypseous 
marls — subordinate beds of concretionary lime- 
stone {cornstone). 

3. In the west of England of very great thick- 
ness and divisible into three groups. 

(i.) Upper group — red conglomerate and 
sandstone. 

(2.) Middle group — cornstone and red marls. 

(3.) Lower group — tilestone, &c. — Fish and 
other fossils — The lower group gra- 
duates into the older strata. 

4. North of England — red conglomerates and 
sandstone resting unconformably on the older 
strata. 

5. Coast of Sutherland, south flank of the 
Grampians, &c. — red conglomerates and sand- 
stone of great thickness. 

6. Caithness — red sandstone — bituminous schist 
with many fossil fish — red conglomerates — Iden- 



42 

tification of these deposits with the old red sand- 
stone of Herefordshire, &c. 

7. Great extent of the formation in Ireland. 

8. Obscure development of this group in 
many parts of the Continent. 



Chapter VI. 

SECONDARY CLASS. 

The lower division — including the Silurian 
and Cambrian systems — the equivalents of 
the principal transition rocks of Werner. 

J. 1. Establishment of the successive groups. 

1 . Mineralogical characters — slaty — highly 
inclined — contorted — more or less crystalline. 
Examples. 

(1.) Greywacke greywacke-slate clay- 
slate — quartz rock — &c. 
(2.) More rarely — chlorite-slate — talc-slate 
mica-slate — hornblende-slate — gneiss, 
&c. &c. 
Hence the difficulty of separating this class 
from the primary divisions, by the evi- 
dence of structure. 

2. Difficulties of classification. 1st. From the 
absence of organic remains through extensive 
tracts: 2d. From the reappearance of similar 
groups of organic remains at great intervals. 



43 

3. Grouping of the whole series only to be 
effected by an extensive comparison of natural 
sections and organic remains. 

4. Section of the Cumbrian Mountains — 
three great natural groups. 

(1.) Highest group — 

{a.) Upper part — greywacke — hard 
siliceous flagstone — coarse grey- 
wacke-slate — a few calcareous 
bands and casts of fossils. 

(h.) Lower part — rocks like the pre- 
ceding — fine greywacke-slate — 
bands of calcareous slate, with 
numerous fossils, &c. 

(2.) Middle group — green quartzose and 
chloritic roofing-slate — porphyry — fel- 
spar rock — trappean breccias, &c. — in 
indefinite alternations, and of very 
great thickness — no fossils. 
3.) Lower group — (Skiddaw slate.) 

(«.) Upper part — dark glossy clay- 
slate — greywacke, &c. — no cal- 
careous bands or fossils. 
{b.) Lower part — porphyritic clay- 
slate, with chiastolite — horn- 
blende-slate with chiastolite — 
mica-slate, finely laminated ; or 
quartzose and coarsely laminated 
— gneiss, &c. 



44 

5. Sections connecting the oldest rocks of 
North Wales with the carboniferous series of 
Shropshire and Flintshire, &p. 

(1.) Upper group — flagstone and greywacke 
slate of Denbighshire — calcareous slate 
and shelly sandstone, with many organic 
remains — rotten micaceous slate passing 
into shale, &c. &c. 

(2.) Middle group — conglomerate and sand- 
stone — clay-slate and greywacke-slate 
— fine chloritic roofing-slate — beds of 
felspar porphyry — calcareous beds with 
organic remains — the whole series rest- 
ing on the limestone of Bala (system 
of the Berwyns). — This series is pro- 
longed into all the north-western por- 
tion of South Wales. {Upper Cam- 
brian system.) 

(3.) Lower group — roofing-slate — felspathic 
and porphyritic series of Caernarvon- 
shire and Merionethshire — organic re- 
mains and calcareous bands rare — the 
whole of vast thickness. {Lower Cam- 
brian system.) 

(4.) Group in Isle of Anglesea and south- 
west coast of Caernarvonshire — chloritic 
slate — mica-slate — quartz rock — white 
crystalline limestone, &c. {Primary 
class.) 

Difficulty in connecting the several divisions 
of the two preceding sections. 



./ 



45 

6. Sections of North and South Devon. 

{a.) North Devon. 

(1.) Culmiferous series — occupying a great 
trough — resting towards the south on the 
granite of Dartmoor — towards the north 
on the slate rocks of Barnstaple, Dul- 
verton, &c. 

(2.) Group of earthy schist — calcareous slate 
full of fossils — shelly sandstone — coarse 
micacious flagstone — coarse greywack^ 
&c. — fossil plants. 

(3.) A great group of chloritic slates alter- 
nating with bands and masses of coarse 
greywacke. 

(4.) Calcareous slates and limestone of 
Ifracombe — many fossils. 

(5.) A very thick group of coarse arenaceous 
structure and generally of a red colour 
— coarse greywackd, rarely passing into 
conglomerate — red and variegated mi- 
caceous flagstone — purple and dark 
shales and slates, &c. — fossils very 
rare. 

(6".) Group of unknown thickness — cal- 
careous slate, &c. alternating with are- 
naceous flagstone, coarse greywacke, 
&c. — many organic remains — Linton 
and valley of the Lyn. 



46 



(b.) South Devon. 

(i.) Upper slate group of very great 
thickness — structure variable — shale 
or earthy slate — grey wack^- slate — 
clay-slate — chloritic-slate, &c. — quartz 
veins — coarse siliceous beds, &c. — no 
beds of limestone — fossils very rare. 

(2.) A group of great thickness — resembling 
No. 5 of the North-Devon section — 
a few organic remains in the schists 
alternating with the coarse red sand- 
stone. 

(3.) Lower slate group of great thickness — 
two great subordinate courses of lime- 
stone (Plymouth and Ashburton series) 
— near the granite the lower slate beds 
metamorphic — many fossils near the 
calcareous bands. 

(4.) Group of chloritic-slate, mica-slate, &c. 
(Bolt Head and Start Point, &c.) — 
relation to the other groups obscure — 
provisionally put in the primary class, 
but perhaps only one of the preceding 
groups become metamorphic. 

N. B. Groups 1, 2, and 3 of this section are 
considered as the equivalents of groups 
3, 5, and 6, of the North Devon section. 
No. 4 not being represented in South 
Devon. 



47 

7. Cornish Sections. 

(1.) Prolongation of the lower South Devon 
group into Cornwall — thinning out of 
the Plymouth limestone — continuation 
of the Ashburton series on both sides 
of the axis of granite. 

(2.) Great varieties of mineral structure — 
near the granite the slate group entirely 
metamorphic — overlaid by the system 
of the Lizard. 

(s.) Calcareous slates, &c. with organic re- 
mains (Whitesand Bay — Loe — Fowey 
— Gerran's Bay — New Quay — High 
Cliff— Padstow—Tintagel— South of 
Launceston — &c. 

8. Identification of the preceding fossilliferous 

systems of Devonshire and Cornwall with the 

Upper Cambrian system. 

N. B. All the preceding sections of this chapter are 
imperfect — no deposits in any of the highest groups 
connecting them with the old red sandstone and 
carboniferous series. 

9. Sections from Caer Caradoc to the Clea 
Hills — from the west flank of the Malvern Hills 
through Ledbury — through the amphitheatre of 
Woolhope, &c. 

10. A complete series established to the base 
of the old red sandstone — Silurian system of 
Mr Murehison. 



48 

J 2. Successive systems aud groups of the lowest 
secondary class. 

1. Silurian system — Upper division. 

(1.) Ludlow Rocks — subdivided into 

(«.) Upper Ludlow rock — grey thin 
bedded arenaceous rock — mica- 
ceous and calcareous — earthy 
texture, &c. 

Fossils. Fish of five new genera — 
Coprolites — Serpuloides gigas — 
Leptcena — Or this — Terehratula 

Orthoceras Bellerophon 

— Homalonotus Knightii, &c. 

{b.) Aymestry limestone- — grey and 
blue argillaceous subcrystalline 
limestone mixed with and pass- 
ing into calcareous slate. 

Fossils. Pentamerus Knightii — 
Lingula Lewisii — Terehratula 

Wilsoni Calymene Blumen- 

hachii, &c. 

(c.) Lower Ludlow rock — dark are- 
naceous flagstone and shale with 
concretions of earthy limestone. 

Fossils. Cardiola Orthocerata, 

many species — Phragmoceras 
— Graptolites — Calymene Blu- 
menhachii — Asaph us Caudatus^ 
&c. . 



49 

(2.) IVenlock limestone. 

(a.) Grey and blue limestone — parts 
concretionary and crystalline. 

Fossils. Corals — Crinoidea — JEuom- 
phalus—Producta—Terehratula 
— Trilobites, several species, &c. 

(b.) Wenlock shale — grey and dark 
coloured argillaceous shale with 
concretions of earthy limestone. 

Fossils. Producta transversalis — 
Spirifer — Terehratula — OrtJio- 
ceras — Asaphus longicaudatus, 
&c. &c. 
2. Lower Silurian. 
(1.) Caradoc Sandstone. 

(a.) Upper — thin bedded impure 
limestone — laminated micaceous 
greenish shelly sandstone. 

Fossils. Bellerophon hilohatus — Or- 
this, several species. Pentamerus 
kevis. P. oblongus. Producta. 
Avicula. Trinucleus (Llhwydd), 
&c. &c. 

{b.) Lower — red, purple, greenish, 
and white freestones ; conglome- 
rates, grits; arenaceous lime- 
stones, &c. &c. 
Fossils. Avicula obliqua. Orthis 
several species — Terebratula un- 
guis — many trilobites of the 



50 

genus Trinudeus. Catenipora 
and other corals. 
<2.) Llandeilo flagstone — Calcareous shale- 
flagstone and limestone. 

Fossils. AsapJiMS Buchii. A. tyran- 
nus. Nucula Icems. Spirifer 
alatus, 8^c. with several species of 
crinoidea, shells, and corals com- 
mon to the Caradoc sandstone. 
Range and extent of the whole system. — Shrop- 
shire, Herefordshire, S. Wales, — Denhigh shire, 
Westmorland, &c.— Foreign localities, &c. 

3. Upper Cambrian System. 
(].) Varieties of structure. 
Rocks of slaty structure. 

(«.) Coarse slate and flagstone— ex- 
foliating parallel to the planes 
of deposit — rarely with casts of 
shells. 

{h.) Fine greywacke-slate and clay- 
slate — cleavage inclined at va- 
rious angles to the true beds. 

(c.) Other varieties — different de- 
grees of induration — alum-slate 
— whetstone-slate — flinty-slate 
— fine chloritic slates like those 
of the lower system, especially 
where the rock is associated with 
trap, &c. 



51 

Rocks not of slaty structure. 

(«.) Conglomerates passing into mill- 
stone and coarse sandstone — 
greywacke — quartz-rock, &c. 

(b.) Great beds and masses, more or 
less concretionary, of limestone. 
— Associated with them are cal- 
careous slates — Corals — Encri- 
nites — Trilohites — Orthocera- 
tites — Or this — Producta — Spi- 
rifer, &c. &c. — Many shells of 
the same species with those of 
the Lower Silurian rocks. 
(2.) Range, extent, &c. 
Examples : 

(«.) Rocks of the Berwyn Hills, 
based on the Bala limestone. — 
This limestone contains Belle- 
rophon hilohatus^ Producta se- 
ricea, and nine species of Orthis 
— all of which are common to 
the lower Silurian system. 

{h.) All the older slate-rocks of South 
Wales including the slate of 
Pembrokeshire. 

(c.) Whole series of North and South 
Devon. 

(</.) Cornish killas — many parts 
mineralized and altered — nu- 
merous organic remains. 
D 



52 

(e.) Other examples — Charnwood fo- 
rest — lower portion of the upper 
group of the Camhrian moun- 
tains — greywack^ chain on the 
border of Scotland, &c. 

The Silurian and Cambrian systems 
appear to be widely extended in 
Scandinavia — various parts of the 
Continent of Europe — North Ame- 
rica, &c. — ^but their limits and fos- 
sils not generally ascertained. 

4. Lower Cambrian Si/stem. 

Clay-slate, often chloritic — greywacke-slate, 
&c. — alternating with trappean rocks. 

(l.) Great development of this series in Eng- 
land — Examples : 
(a.) Central schistose group of North Wales. 
In Caernarvonshire and Merionethshire 
composed as follows, viz. : — Various por- 
phyritic rocks with a base of compact 
felspar; greenstone in beds and irregular 
masses ; felspathic and quartzose beds in 
globular concretions ; pseudo-conglome- 
rates, and irregularly brecciated masses 
passing into porphyry, &c. &c. — alter- 
nating indefinitely, with quartzose and 
chloritic slaty masses; quartzose beds 
passing into granular quartz rock ; 
felspathic slate, brecciated or in minute 
contortions ; talc-slate passing into por- 



58 

phyry; greywacke with casts of Tere- 
bratulas, very rarely with impressions of 
corals ; great masses of greywacke-slate 
and clay-slate, both soft and indurated, 
and with a cleavage inclined to the 
planes of dip, &c. — the whole series 
based upon greywacke-slate and clay- 
slate alternating with two or three 
zones of porphyritic and felspathic rocks. 
— In Caernarvonshire and Merioneth- 
shire this system is bent into great 
curves producing a series of anticlinal 
and synclinal lines parallel to the bear- 
ing of the chain ; and in some places 
abuts against, or is irregularly inter- 
rupted by, protruding masses of syenite 
and porphyry. 
(A . ) Cen tral schistose group of Cumherland, 
JVestmorland^ and Lancashire, com- 
posed as follows, viz. : Various porphyritic 
rocks with a base of compact felspar; 
hornstone, hornstone-slates; greenstone; 
concretionary beds and pseudo-conglo- 
merates ; coarse brecciated masses pass- 
ing into and blended with porphyries, 
&c. &c. — alternating indefinitely with 
coarse quartzose chloritic beds, more or 
less fissile ; and with fine quartzose and 
chloritic masses cleaving into thin laminae 
parallel to the strike, but inclined to the 

D2 



34 

planes of dip, &c. — the whole system 
stratified, having a remarkable constancy 
in its strike and dip, and without traces 
of organic remains — In Cumberland this 
group sometimes rests immediately upon 
the third schistose group — sometimes 
upon granite or syenite, irregularly pro- 
truded between the second and third 
groups. 
(c.) Other localities. 
(2.) Upper and lower limits of this series ill 
defined — minerals — Fossils very rare. 



Chapter VII. 

PRIMARY CLASS. 

Sedimentary Rocks without Organic Remains 
inferior to all the preceding groups. 

British Examples of this Class. 

1. Cumberland. 

(a.) Soft dark-coloured glossy clay-slate 
(Skiddaw-slate) — greywacke-slate with 
subordinate beds of coarse greywacke, 
&c. — This group contains numerous 
quartz veins — does not effervesce with 
acids — is ,iiidurated and changed in 



55 

structure near its junction with masses 
of porphyry and syenite, by which it is 
penetrated, traversed, and overlaid — 
contains no organic remains — rests on 
chiastolite-slate, through which it passes 
into an inferior crystalline group. 
(b.) A group interposed between the pre- 
ceding and the central granite of Skid- 
daw forest — composed nearly as follows: 
(1.) Clay-slate with crystals of chias- 

tolite. 
(2.) Hornblende - slate mixed with 
slate made up of matted crys- 
tals of chiastolite. 
(3.) Mica-slate — finely laminated — 
or quartzose and coarsely lami- 
nated. 
(4.) Irregularly laminated rocks ap- 
proaching the character of gneiss^ 
The greater part of this group con- 
sidered m.etamorphic. 
2. Anglesea and S.W. coast of Caernarvon- 
shire — a group inferior to the system of Snow- 
donia, and composed principally of chlorite-slate. 
(«.) Chlorite-slate— finely laminated — quartz- 
ose — contorted — sometimes micaceous 
and passing into quartzose mica-slate, 
&c. 
(b.) Contorted quartz-rock — separated into 
slaty masses by flakes of mica ranged 



56 

in parallel planes inclined to the planes 
of stratification. (Holyhead Mount.) 
(c.) Chlorite- slate penetrated hy veins of 
carbonate of lime — passing into amor- 
phous masses of serpentine and vert- 
antique (Anglesea) — similar masses as- 
sociated with jasper (Coast of Caernar- 
vonshire.) 
(d.) Chlorite- slate j)enetrated by veins of 
carbonate of lime — passing into beds 
of crystalline limestone penetrated by 
chlorite — associated with masses of 
jasper and serpentine. (S.W. coast of 
Caernarvonshire. ) 

This group is associated with, and 

traversed by, many masses and 

dykes of trap. 

3. Other examples, of highly crystalline 

stratified rocks associated with various groups of 

the secondary series — generally near un stratified 

rocks. 

(i.) Hornblende-slate and mica-slate of the 
Lizard (associated with serpentine, green- 
stone, diallage rock, &c.) overlying killas 
and greywacke. 
(2.) Crystalline rocks near the junction of 

the granite and killas of Cornwall. 
(3.) Crystalline rocks near the junction of 
the Culm measures with the granite 
of Dartmoor. 



57 

(4.) White Marble of the Isle of Sky at 

the junction of the syenite and lias. 
(5.) Crystalline rocks among the older and 
newer secondary groups of the Alps, &c. 
Hence the impossibility of deter- 
mining the epoch of the old 
crystalline groups by mere mine- 
ral structure. 

4. Examples of crystalline rocks, largely de- 
veloped, and arranged provisionally in the primary 
class. 

(1.) Mica and chlorite-slate of Bolt Head. 
(2.) Formations of chlorite-slate — talc-slate 

— mica-slate — hornblende-slate, &c. 
(3.) Crystalline limestone — common and do- 

lomitic — generally subordinate to other 

groups. 
(4.) Quartz-rock — great development in the 

Highlands of Scotland. 
(5.) Gneiss — great development in Scotland. 

Varieties of structure — subordinate 
mineral masses — contortions — re- 
markable localities, &c. 

5. Remarkable successions of different primary 
groups in different natural sections. — Conclusion. 



PART III. 

IGNEOUS AND UNSTRATIFIED ROCKS, &c. 



Chapter I. 

Introduction. 

1. Prevailing characters of rocks of this 
class — modes of their distribution — 

(i.) In irregular overlying masses: 

(2.) In protuberances and in great tabular 
masses interrupting the regular succes- 
sion of the stratified rocks : 

(3.) In veins: 

(4.) In great central masses producing anti- 
clinal lines and often forming the axes 
of moiintain-chains : 

(5.) In regions unconnected with stratified 
rocks. 

2. Great variety of minerals and mineral struc- 
ture in the rocks of this class — Examples of some 
of the modifications : 

(i.) Rocks of simple or nearly simple struc- 
ture. 

(«.) Claystone in various states of 
induration ; 



59 

(b.) Clinkstone ; 
(c.) Compact felspar; 
(d.) Basalt; 
(e.) Pitch stone ; 
(Jl) Serpentine; 
&c. &c. 
(2.) Further subdivisions arising out of the 
modifications of the preceding species — 
Examples : 

(«.) Felspar porphyry; 
(b.) Pitchstone porphyry; 
(c.) Pearlstone; 
(d.) Amygdaloids; 
(e.) Trachyte; 
(yi) Trachytic porphyry; 
&c. &c. 
(3.) Binary compounds, more or less distinctly 
granular — Examples : 

(«.) Greenstone — becoming compact 
and passing into a basaltic form. 
(b.) Augite rock {Dolerite, Mela- 
phyre) — often passing into a 
basaltic form. 
(c.) T>\3\\ageYock{Euphotide) — pass- 
ing into serpentine. 
&c. &c. 
(4.) Granitoid rocks — generally composed 
of more than two constituents — with 
felspar often distinctly crystallized — 
Examples — granite — syenite — &c. 



60 

(5.) Other modifications — rocks of globular 
and columnar structure. 

3. The unstratified rocks associated with strati- 
fied rocks of different epochs — pass into and replace 
each other — their place in the series not defined 
by their structure. 

4. General agreement of the series of unstrati- 
fied rocks with true volcanic products. — Conclu- 
sion. 



Chapter II. 

Unstratified Rocks associated with tertiary 
deposits. 

1. Streams of basaltic lava, and masses of 
volcanic breccia, following the course of existing 
valleys — sometimes connected with existing cra- 
ters. Examples — valleys of Auvergne and Viverais 
— valleys on the right bank of the Rhine near 
Andernach — &c. 

2. Portions of more ancient streams of lava 
anterior to the existing valleys, masses of volcanic 
breccia, &c., overlying and sometimes alternating 
with tertiary strata. — Examples : 

(1.) Older basaltic rocks of Auvergne and 
Viverais. 

(2.) Volcanic breccias and basaltic lavas over- 
lying and sometimes alternating with the 
newer tertiary deposits of Styria. 



61 

(3.) Basaltic plateaux of Hessia. 

3. Great masses and protuberances, more or less 
granitoid and porphyritic — sometimes overlying 
tertiary deposits — ^^sometimes producing anticlinal 
lines. — Examples : 

(1.) Trachytic domes of Auvergne. 
(2.) Trachytic masses of Styria and Hungary. 
(3.) Trachytic masses on the right bank of 
the Rhine — (Drachenfels.) 

4. Subaerial and subaqueous volcanic pro- 
ducts — resulting varieties of trap-rocks. 



Chapter III. 

Trap Rocks associated with the upper secondary 
strata. 

1. Overlying masses — dykes — ^irregular ta- 
bular masses alternating with secondary strata. — 
Examples in detailed sections. 

(1.) North of Ireland. 
(2.) Hebrides. 

(3.) Derbyshire, Durham, and Northumber- 
land. 

2. Great complications of mineral structure — 
Examples from the Isle of Arran. 

3. Effects produced on various secondary de- 
posits by the intrusion of trap. 



62 

Examples : 

(1 .) Siliceous schist (indurated shale)— North 
of Ireland ; Isle of Sky ; Isle of MulL 

(2.) Granular marble — jasper — irregularly 
crystallized masses with crystals of 
garnet and analcime, &c. — Isle of 
Anglesea — Teesdale. 

(3.) Anthracite in contact with the trap- 
dykes of various coal-fields. 
&c. &c. 

4. Mountain masses of trap — structure often 
granular or porphyritic — passing into the other 
varieties. — Examples : 

(i.) Syenite and hypersthene mountains of 
the Isle of Sky — effects produced by 
their contact with the lias. 

(2.) Trap-rocks of the valley of the Tweed 
— granitic and porphyritic rocks of the 
Cheviots — some of the masses prior to 
the old red conglomerates — other masses 
of like structure posterior to the lower 
portion of coal-measures — basaltic rocks. 

5. Black augitic porphyry — red felspathic 
porphyry — serpentine, &c. — many epochs of erup- 
tion — difficulty of defining any of them by 
mineral structure. 



63 



Chapter IV. 

Unstratijied Rocks associated with the lower 
secondary {or transitiofi) groups. 

1. Dykes and irregular tabular masses inter- 
rupting the succession of the stratified rocks — 
great variety of their structure. 

2. Mountain masses irregularly protruded 
amongst, or overlying, the stratified rocks — 
Examples : 

(1.) Basalt syenite and granite of Christiana 
associated with orthoceratite-limestone. 

(2.) Syenite and porphyry of Cumberland 
irregularly traversing and overlying the 
Skiddaw-slate. 

(3.) Granite of Shap protruded between the 
upper and central stratified group of the 
Cumbrian mountains. 

(4.) Syenite of the Rivals and other mount- 
ains of Caernarvonshire. 

(5.) Serpentine of the Lizard — associated 
with porphyry, syenite, hornblende- 
slate, &c. — overlying greywackd-slate. 

3. Mountain masses producing anticlinal lines 
and forming the axes of primary chains. — 
Examples : 

(1.) Granitic chain of Cornwall — relations of 
the crystalline central masses to the 



64 

slate-rocks — varieties of mineral struc- 
ture — difFerent periods of production. 
(a.) The great masses of central gra- 
nite posterior to the slate. 
(b.) Dykes and masses of porphyry 
(elvans) posterior to the central 
granite. 
(2.) Central granite of the Hartz — its re- 
lation to the surrounding formations — 
proofs of its recent protrusion. 
&c. &c. 



Chapter V. 

Ci-ystalline masses interrupting or forming the 
base of the primary groups. 

1. Great complexity of the lowest stratified 
groups — modes of their association with unstrati- 
fied masses exhibited in sections. 

2. Crystalline structure of some of the strati- 
fied groups superinduced by the action of the 
unstratified — examples of remarkable changes of 
structure probably produced by the action of 
granitic masses. 

3. Granitic veins traversing primary strata — 
circumstances under which they are most abund- 
ant theory of their origin^ — various examples 

from the primary mountains of Scotland. 



65 

4. Central granite — examples of its associa- 
tion with the lowest stratified groups. 

5. Varieties of granite : 

(i). From the changes of aggregation — 
porphyritic — globular — graphic — &c. 

(2.) From the addition of a new constituent. 

(3.) From the suppression or replacement of 
a constituent. — Examples : 

6. Decomposition of granite — extent of gra- 
nitic countries — remarkable localities. 

7. Different epochs of the production of 
granite — not defined by the structure of the 
rock — granite veins — proofs of their injection in 
a fluid state exhibited in detailed sections. 



Chapter VI. 

Successive periods of elevation — metalliferous 
veins — theories of the earth. 

1. Review of the relations of stratified and 
unstratified rocks, 

2. Unstratified masses generally the result of 
igneous action — produced during many successive 
periods — in different degrees of fusion — some- 
times protruded in a solid form. 

3. Different periods of elevation — their in- 
fluence on the physical geography of Europe. 



66 

4. Geological connexions of some of the prin- 
cipal mountain-chains of Europe — manner of in- 
vestigating their several periods of elevation — 
sketch of the theory of M. Elie de Beaumont. 

5. Physical geography of the British Isles 
connected with different periods of elevation. 

6. Classification of some of the great faults 
traversing the British stratified deposits — differ- 
ent modes in which they are filled. 

7. Smaller faults produced during periods of 
elevation — metalliferous veins — theories of their 
formation — &c. 

8. Sacred theories of Burnet, Woodward, and 
other writers — formation of geological collections 
— importance of the old geological cabinets in 
the University of Cambridge. 

9. Theories of Werner and Hutton. 

10. Present condition of Geology, considered 
both as a practical and speculative science — 
desiderata — Conclusion. 



QE Sedgwick, Adam 

35 A syllabus of a course 

S4 of lectures on geology 

1837 



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